So what if the AT has a bug and isn't picking up the information right?
Tests fail for this reason based on an AT vendor issue. Platforms where
accessibility services are provided should provide inspection tools so
this can be independently validated by developers, and acceptance and
quality assurance testers.

Looking at the WCAG 2.0 information about "accessibility supported", I
don't think the existence of inspection tools are necessary to consider
the technology accessibility supported.

It seems to me that as long as the technology allows an application to
pass information through an accessibility framework to user
agents/assistive technology and that information is then passed along to
the user, then the technology could be considered accessibility
supported.

If my understanding is correct, then I would think the only thing that
is necessary to determine if a technology is accessibility supported
would be to set up a series of test cases using the technology to see if
accessibility information is conveyed to the user. An inspection tool
would be useful in determining where any failures occur, but the test
case would just have to fail for the technology to be considered not
accessibility supported.

Question:
When is a system considered accessibility supported, or "open/closed"?.

If a system has available assistive technology, available accessibility
services for applications to utilize, but no inspection tools are
available to determine if indeed object information is being used, and
if so, is it accurate, is the platform considered accessibility
supported or open/closed?

So, for Apple platform what inspection tools are there?
So for Android, what inspection tools are there?
So, for Blackberry what inspection tools are there?
So, for WebOS what inspection tools are there, or for that matter what
accessibility services are there?